3.4.1. Processing of Aluminum Alloy AlCuMg2

The objects of study during the tests were the wear of three-flute end mills made of 6WH10F hard alloy (Figure 2) and the surface roughness of machined workpieces in the form of bars made of aluminum alloy AlCuMg2.

Figure 10 shows the experimentally obtained dependence of the flank wear chamfer (*h*) of end mills on the tool time (*T*) with various coatings, uncoated, with DLC and (CrAlSi)N/DLC.

**Figure 10.** Dependence of the wear chamfer size on the flank surface of the end mills on the operating time when machining the aluminum alloy AlCuMg2 with end mills with different coatings.

These data demonstrate a pronounced positive effect of DLCs on the resistance of milling cutters (up to the maximum wear value of 0.4 mm) when processing the aluminum alloy. The development of the wear chamfer on the flank surface due to the coating slows down many times; if the tool life without coating was 99 min, the tool life with DLC is now 342 min. Optical images (Figure 11) showing the general appearance of the worn chamfer on the flank surface of the milling cutters after 72 min of operation, illustrating the above well—the coating significantly slows down the development of wear processes. Thus, we can conclude that the durability of a DLC-coated cutter is 3.45 times higher than that of an uncoated cutter when processing an aluminum alloy AlCuMg2.

**Figure 11.** The size of flank wear chamfer after 72 min of operation when processing aluminum alloy AlCuMg2 with end mills: (**a**) uncoated, 250.51 μm; and (**b**) with a single-layer DLC, 48.65 μm.

An interesting fact is noteworthy, the application of a (CrAlSi)N sublayer before the formation of the DLC does not have any effect on the cutter's behavior during operation (Figure 10).

The experimental data obtained during the tests (Figure 12) show that when machining an aluminum alloy with uncoated end mills, the surface roughness (*R*) increases significantly after 27 min of operation and at the time of tool failure (99 min), is about 3 μm. When cutting an aluminum alloy with a diamond-like coated cutter, the roughness of the surface of the processed workpiece during 150 min of tool operation practically does not change and, on average, is 1.3 μm. At the moment of failure of the coated tool (342 min), the average roughness value was 2.5 μm. It is important to note

that even in the first minutes of operation of the still unworn cutter, there is a noticeable difference in the surface quality of the workpiece, achieved by the tool without coating and with DLC of 1.75 μm and 1.25 μm, respectively. Experimental data presented in Figure 12 show that the deposition of a sublayer (CrAlSi)N before forming the DLC does not significantly affect the change in the roughness of the treated surface during the end mill operation.

**Figure 12.** Dependences of the roughness of the treated surface of a workpiece made of aluminum alloy AlCuMg2 on the operating time of end mills with different coatings.
